Benefits of Soy: A Mixed Bag

July 1, 2011 -- Soy appears to help midlife women deal with hot flashes and night sweats, according to a new report.

However, the evidence for other potential benefits of soy -- such as effects on heart and bone health -- is not clear, a panel of experts has concluded.

''It gets a good score for [menopausal] symptoms," says researcher Wulf Utian, MD, PhD, ScD, a consultant in women's health and executive director emeritus of the North American Menopause Society. ''But the data is really not strong to give a high score for any of the rest."

With a working group of experts in the field, Utian combed through evidence during a two-day symposium in late 2010 to evaluate the health benefits of soy for women at midlife.

They looked at research evaluating soy from foods and supplements. Soy's isoflavones are credited with producing the healthy benefits. The isoflavones were first considered to be ''plant estrogens" and estrogen-like in action. But experts now believe they may also work in other ways, such as having antioxidant properties.

Among the findings of the working group:

Soy relieved certain menopausal symptoms. Utian says the relief from hot flashes is typically moderate. According to research, soy does not work as well as hormone therapy but was better than placebo, Utian tells WebMD. "If you give estrogen a 9 out of 10 score, and placebo 4 of 10, soy would be about 6.5."

Supplements with a higher proportion of the isoflavone known as genistein or increased S(-)-equol, which is made by intestinal bacteria from the isoflavone daidzein, seem to provide more benefits than other products.

Soy from foods is linked with lower risks of breast and endometrial cancer in studies.

The benefit of soy intake on bones is not yet proven. "On bone health, we really didn't find adequate evidence to recommend its use for preventing or reducing the risk of osteoporosis and osteoporotic fracture," Utian says.